What is Insomnia Disorder?

Depending on how we define insomnia, up to 50% of the population experiences some type of sleep problem. Insomnia disorder is defined as difficulty falling asleep, staying asleep, or waking up too early, at least 3 days a week, for a significant duration (>3 months). Insomnia is a 24-hour disorder and impacts the daytime as well, such as mood, fatigue, anxiety, concentration, and memory issues.

When thinking about insomnia, we need to differentiate between acute and chronic insomnia. Acute insomnia, which only lasts a few weeks to a couple months, usually occurs during times of stress. For example, if you are studying for your MCAT exam and very stressed about doing well, it isn’t surprising that sleep takes a dip. This is completely normal and sleep usually gets better after the stress (in this case, the exam) is over. On the hand, chronic insomnia is when sleep disturbances continue well after any stressors that may have initially affected sleep has come and gone. But why is this? What causes acute insomnia to become chronic?  

The 3P Model of Insomnia

Spielman and colleagues (1987) developed an elegant model to understand how chronic insomnia develops, known as the 3P model of insomnia. The 3P stands for: Predisposing, Precipitating, and Perpetuating factors.

Predisposing factors are factors that make someone more vulnerable to insomnia. For example, people who worry more or are more reactive to stress might be more likely to experience sleep disturbances when stressful events happen. Precipitating factors are the initial stressful event that caused your sleep problems in the beginning. These factors can be both positive (planning a wedding, having a baby, starting a new job) and negative (loss of a relationship, failing an exam, death of a loved one). As we talked about, usually the sleep problems are short-term and go away once you’ve gotten through the stressful part. However, for some people, the insomnia remains. This is because of perpetuating factors – behaviours and ways of thinking about our sleep that maintains our sleep problem. Perpetuating factors are KEY to understanding why someone has chronic insomnia and they are what mental health professionals focus on when helping people with insomnia.

Below, I talk about the three main causes of chronic insomnia in turn.

This is the 3P model at work. Predisposing factors make it easier for precipitating factors (stressful events) to trigger an initial insomnia episode. For some people, insomnia goes back down after the precipitating event is over. On the other hand, perpetuating factors can maintain our sleep problems. This is known as chronic insomnia

1. Low Sleep Drive

Sleep drive (or sleep pressure) is our propensity to fall asleep at any given moment. Assuming you just woke up and had a great night’s sleep (which is probably rare since you’re reading this article), then your sleep drive is very low, and you have little desire to sleep more. Throughout the day, as you engage in work and other activities, you build up more sleep drive, such that by the end of the night you have a lot of sleep drive to expend. This pressure to sleep is what provides us with the restorative deep sleep that we need. However, for people with insomnia, they engage in behaviours that impact this build-up of sleep drive because they are so tired. They will often cancel plans, spend more time during the day resting, try to sleep-in or go to bed early before they are actually sleepy (people with insomnia are “tired” not “sleepy”). These behaviours are very reasonable, but they impede our ability to develop sleep drive and maintains the pattern of unrefreshing sleep.

Model showing how sleep drive builds up throughout the day and can be reduced.
A typical 7-11pm schedule.
Sleep drive can be affected by naps, sleeping in, reducing activities.

2. Social Jetlag (Irregular Circadian Rhythm)

Have you ever travelled into a different time zone and found that everything gets thrown off? For example, you were sleepy and awake at odd hours; hunger signals were thrown off; and everything feels irregular? This “jetlag” occurs when our internal circadian clock is mismatched to the clock on the wall. Jetlag is something most people are familiar with. However, did you know that jetlag can occur without travelling? When we wake up at different hours throughout the week, we throw our body into a state of jetlag. For example, if on Monday we wake up at 8:00am and on Sunday we wake up at 11:00am, the 3-hour time difference creates the same jetlag as somebody travelling from California to New York! The differences in bed and rise times between weekdays and weekends may also be why Mondays are particularly hard for people going to work (besides the obvious fact that you have to go to work!).

A person confidently saying “I have a regular schedule!”, while simultaneously having a 5 hour difference in risetime on weekdays and weekends. This jetlag is equivalent to travelling from North America to Europe (yikes)!

3. Conditioned Arousal

Ever heard of Pavlov and his dog? A scientist named Ivan Pavlov rang a bell every time he was feeding his dogs. Over time, he realized that the dogs would salivate when they heard the bell even if there was no food. He realized that the dogs had associated the ringing of the bell with food (known as classical conditioning). Humans aren’t so different from animals in this way – we can also begin to associated things that are normally not associated together.

So why is this important? People with insomnia are often extremely anxious/worried about their sleep. This puts them in a heightened fight-or-flight response, especially during the nighttime. Unsurprisingly, they spend a lot of time in bed, awake and in distress (worrying, ruminating, thinking “why can’t I sleep?”). Over time, they begin to associate the bed with wakefulness and distress rather than for sleep. In my clinical practice, that’s why people with insomnia often say that “I will often go to bed feeling sleepy, but the second my head hits the pillow – it’s a light switch and my brain is suddenly wide awake”). This is the conditioned arousal at work.

My face when I hear the sound of a bell ringing but there’s no food around

Tips to breaking the insomnia cycle

Now that we know what causes insomnia, we can talk about how to fix it!

1. First, we need to break the cycle by building up the sleep drive! People often try to make up for their loss of sleep the previous night. While this makes complete sense, it actually creates a vicious cycle because its impacting our sleep drive for the next night. By disregarding how the last night went, we can focus on building up sleep drive for the next night. This means not sleeping in, generally avoiding naps, being reasonably active even if you’re tired (e.g., yoga, taking a walk, spending time with friends), and going to bed when you are sleepy.

2. Second, keep to a regular rhythm. This means generally staying consistent with your bed times and rise times. Regular exposure to light is perhaps the most important factor in cueing your internal clock and making sure that it stays consistent with the external clock. So once you get up, try to get some sunlight if you can!

3. The bed is only for sleep. In order to break the association between the bed and wakefulness, and strengthen the relationship between the bed and sleepiness, we need to remove wakeful activities from the bedroom environment. If you enjoy reading or watching TV before bed, try to do so somewhere else – such as a comfy couch and go to bed only when you are sleepy. If you notice that sleep is not coming and the train of worries is starting to come out, then get out of bed, do something pleasant, and then get back into bed once you are sleepy again.

And that’s it! I know that these tips are much easier said than done. However, they are extremely effective if used together for a consistent period of time to improve your sleep. These are evidence-based strategies that target our understanding of what causes and maintains insomnia.

If you are interested in other strategies for sleep, see here for strategies to manage fatigue and to manage worrying in bed.

I hope this has been helpful!

Best wishes,

P